The present invention relates to excavating equipment, and in particular to a backfill conveyor for trenches and the like.
Backfill conveyors are used in excavating long ditches, trenches, or the like, in which pipes, wires, cables, and other similar elongate objects are buried in the ground. Such conveyors typically have an upstream end positioned adjacent to the point at which the trench is being or has been dug, such that a backhoe, or other trenching machine can place the excavated dirt into a hopper associated with the conveyor or directly onto the conveyor. The conveyor extends along the open trench, wherein the pipe is laid, and the downstream end of the conveyor straddles the sides of the trench and backfills the trench with the excavated material. The conveyor and trencher are moved intermittently along the trench to various set up points so that as the pipe is positioned in the trench, it is buried in the ground in a substantially continuous process. Such continuous pipe laying arrangements not only eliminate the need to clean up numerous dirt piles along the sides of the trench, but they also minimize the amount of exposed, open trench, thereby alleviating the associated safety hazards and risk of vandalism.
Trench conveyors of the type disclosed above must be relatively long, in the nature of 50 to 100 feet, to insure that there is sufficient open trench in which to lay and position the pipe. As a result, it is quite difficult to securely support such a long coveyor segment along the trench, particularly in the conveying mode, wherein heavy dirt is being continuously carried along the conveyor. One arrangement for supporting a trench conveyor is disclosed in U.S. Pat. No. 3,583,186 to Horton, and comprises a pair of spaced apart wheels which straddle the sides of the ditch and support the discharge end of the conveyor above the ground. However, because the earth beneath the sides of the ditch is often very soft and uneven, such devices can become stuck and/or tip over. Further, the wheels must often be manipulated to avoid obstruction with objects disposed alongside of the ditch, such as trees, utility poles, pipes, wires, etc. Also, the lateral position of the discharge end of the conveyor over the open ditch is not easily adjusted to accommodate the side-to-side filling of very wide ditches.
Another problem heretofore experienced with trench conveyors relates to the ability of the device to adjust the elevation of the conveyor over the ditch and surrounding terrain. For example, in the laying of large drainage or sewer pipes, an earth moving device, such as a relatively small bulldozer must be used in the backfilling operation. In such circumstances, the ditch is sufficiently wide to bodily receive the bulldozer therein, and the bulldozer pushes the dirt discharged from the conveyor in an upstream direction into the trench to carefully cover the laid pipe and pack the dirt around the pipe to insure that it is securely anchored in position in the ground before the remainder of the ditch is filled. The bulldozer must travel under the downstream end of the conveyor to spread and compact the dirt thereunder. Hence, it is quite advantageous to have a conveyor mechanism which is capable of easily varying the elevation of the conveyor discharge end to provide sufficient clearance for the backfill bulldozer to pass thereunder.
Some integral pipe laying machines, such as that disclosed in U.S. Pat. No. 3,292,379 to McElvany, have a built-in trencher and include a jib with cables on which a conveyor is suspended to backfill the trench. However, in these devices, the cables on which the conveyor is suspended are positioned overhead, and thereby prevent the conveyor from being loaded from the top or upper side, as is required when separate trench conveyor units are used with backhoes, front end loaders, cranes, or other earth digging equipment.